The present invention relates to a fluorine-containing diene having two unsaturated bonds, its production method and its polymer.
As a fluorine-containing diene having two carbon-carbon unsaturated double bonds (hereinafter referred to as unsaturated bonds), CF2xe2x95x90CF(CF2)kOCFxe2x95x90CF2 (wherein k is an integer of from 1 to 3) has been known (JP-A-1-14843). By cyclic polymerization of this compound, an amorphous polymer can be obtained, which has high elastic modulus, yield elongation in tension and breaking extension, which is less likely to break and is excellent in impact resistance. It also has a high transparency, and it can thereby be used as a material for optical components or optical devices such as optical waveguides or optical fibers. However, in a case where an optical resin material is obtained by using this polymer, since the polymer has a low glass transition temperature, the optical properties tend to change by a long-term use at a high temperature.
It is an object of the present invention to provide a polymer which maintains mechanical properties of the above amorphous polymer and has a higher glass transition temperature, and can thereby be an optical resin material excellent in heat resistance, and a fluorine-containing diene having two unsaturated bonds to give such a polymer.
The present invention provides a fluorine-containing diene represented by the following formula 1, its production method and its polymer, a fluorine-containing compound represented by the following formula 2, a method of producing the fluorine-containing diene represented by the following formula 1, which comprises dehalogenating the fluorine-containing compound represented by the formula 2, and a polymer which contains a polymer formed by polymerization of the fluorine-containing diene represented by the formula 1 in monomer units:
CF2xe2x95x90CF(CF2)nCXYOCFxe2x95x90CF2xe2x80x83xe2x80x83Formula 1 
CF2Z1CFZ2(CF2)nCXYOCFZ3CF2Z4xe2x80x83xe2x80x83Formula 2 
wherein each of X and Y which are independent of each other, is an atom selected from a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, provided that X and Y are neither simultaneously hydrogen atoms nor simultaneously fluorine atoms, each of Z1, Z2, Z3 and Z4 which are independent of one another, is a halogen atom selected from a chlorine atom, a bromine atom and an iodine atom, and n is an integer of from 1 to 3.
With respect to X and Y in the formulae 1 and 2, preferably at least one is a chlorine atom, particularly preferably both are chlorine atoms or one is a chlorine atom and the other is a fluorine atom. Particularly preferably, one is a chlorine atom and the other is a fluorine atom. Further, with respect to Z1, Z2, Z3 and Z4, preferably at least one is a chlorine atom, particularly preferably all are chlorine atoms. A chlorine atom strongly connects with a carbon atom as compared with a bromine atom and an iodine atom, such being favorable in view of stability of a compound, and in synthesis of the compound of the present invention and in polymerization of the fluorine-containing diene represented by the formula 1, a reaction such as release of a halogen atom is less likely to take place. Further, the desired dehalogenation reaction can easily be carried out as compared with a case of a fluorine atom or a hydrogen atom. Here, the carbon atom to which X and Y are bonded, is adjacent to an oxygen atom and a difluoromethylene group, whereby a dehalogenation reaction hardly takes place, and the stability is high even if X or Y is a chlorine atom.
The fluorine-containing compound represented by the formula 2 (hereinafter sometimes referred to as a fluorine compound (2)), wherein each of X, Y, Z, Z2, Z3 and Z4 is a chlorine atom, can be produced, for example, by the following method. Namely, iodine chloride and trifluorochloroethylene are reacted at a low temperature to produce a compound (a) represented by the formula 3, which is reacted with a predetermined amount of tetrafluoroethylene in the presence of a radical initiator to produce a compound (b) represented by the formula 4, which is oxidized by fuming sulfuric acid to obtain a compound (c) represented by the formula 5, followed by alkylesterification to produce a compound (d) represented by the formula 6 (wherein R is an alkyl group).
The compound (d) is reduced by e.g. sodium borohydride to produce a compound (e) represented by the formula 7, then this compound (e) is reacted with a metal hydride, and the resulting metal alkoxide is reacted with tetrafluoroethylene to produce a compound (f) represented by the formula 8. The compound (f) is chlorinated so that every hydrogen atom in the compound (f) is replaced by a chlorine atom, and chlorine atoms are added to the unsaturated bond to obtain the desired fluorine-containing compound represented by the formula 9 i.e. the fluorine-containing compound represented by the formula 2, wherein each of X, Y, Z1, Z2, Z3 and Z4 is a chlorine atom (hereinafter referred to as a compound (g)). Here, in this method, by making tetrafluoroethylene react with the compound (a) to produce the compound (b), the desired compound wherein n is 1 or 3 can be obtained. The desired compound wherein n is 2 can be obtained by another known method to produce the compound represented by the formula 5 wherein n is 2, and then conducting the same operation as mentioned above.
CF2ClCFClIxe2x80x83xe2x80x83Formula 3 
CF2ClCFCl(CF2)n+1Ixe2x80x83xe2x80x83Formula 4 
CF2ClCFCl(CF2)nCOFxe2x80x83xe2x80x83Formula 5 
CF2ClCFCl(CF2)nCOORxe2x80x83xe2x80x83Formula 6 
CF2ClCFCl(CF2)nCH2OHxe2x80x83xe2x80x83Formula 7 
CF2ClCFCl(CF2)nCH2OCFxe2x95x90CF2xe2x80x83xe2x80x83Formula 8 
CF2ClCFCl(CF2)nCCl2OCFClCF2Clxe2x80x83xe2x80x83Formula 9 
Further, by changing conditions of the chlorination in the chlorination step to obtain the compound (g), the chlorine-containing compound represented by the formula 2, wherein X is a hydrogen atom, Y is a chlorine atom, and each of Z1, Z2, Z3 and Z4 is a chlorine atom (a compound represented by the following formula 10), can be produced. For example, by partial chlorination by adjusting the feed amount of a chlorine gas or the ultraviolet irradiation intensity in the chlorination step as mentioned hereinafter, one of the two hydrogen atoms in the compound (f) can be replaced by a chlorine atom. Further, by partial fluorination of the compound (g) represented by the formula 9, the fluorine-containing compound represented by the formula 2, wherein X is a fluorine atom, Y is a chlorine atom and each of Z1, Z2, Z3 and Z4 is a chlorine atom (a compound represented by the following formula 11, hereinafter sometimes referred to as a compound (h)) can be produced.
CF2ClCFCl(CF2)nCHClCOFClCF2Clxe2x80x83xe2x80x83Formula 10 
CF2ClCFCl(CF2)nCFClOCFClCF2Clxe2x80x83xe2x80x83Formula 11 
By the reaction of iodine chloride and trifluorochloroethylene is carried out by a method disclosed in a literature (J. Am. Chem. Soc., 83, 2495 (1981)) at a low temperature, preferably from xe2x88x928xc2x0 C. to 0xc2x0 C., the compound (a) is selectively formed. The reaction of the compound (a) and tetrafluoroethylene is carried out in the presence of a radical initiator such as a peroxide or an azo compound, usually at from 20 to 150xc2x0 C., preferably from 60 to 100xc2x0 C., while keeping tetrafluoroethylene under at most 1 MPa, preferably at most 0.5 MPa, to obtain the compound (b).
The production of the compound (c) by oxidation of the compound (b) is carried out, for example, by fuming sulfuric acid. The concentration of fuming sulfuric acid may optionally be selected. The reaction temperature varies depending upon the concentration of the fuming sulfuric acid, but is from 40 to 100xc2x0 C., preferably from 60 to 80xc2x0 C., when the concentration is 60 mass %, for example. The alkylesterification of the compound (c) is carried out by dropwise adding the compound (c) to an alkanol, for example. By reacting an alkanol with the compound (c) at a low temperature, preferably at from 0xc2x0 C. to 20xc2x0 C., the corresponding compound (d) can be obtained. As the alkanol, preferred is an alkanol having a carbon number of at most 4. The reduction reaction of the compound (d) is carried out, for example, by sodium borohydride or lithium aluminum hydride. The reaction is carried out at a low temperature, preferably from 0xc2x0 C. to 20xc2x0 C. to obtain the compound (e) as the corresponding fluorine-containing alcohol.
With the compound (e), a metal hydride such as sodium hydride or lithium hydride is reacted at a low temperature, preferably at from 0xc2x0 C. to 20xc2x0 C., to produce a fluorine-containing alkoxide corresponding to the compound (e). As the metal atom in the fluorine-containing alkoxide, in addition to sodium or lithium, an alkali metal atom such as potassium or cesium, or a silver atom, may, for example, be mentioned. As a reaction solvent, a non-cyclic or cyclic ether type solvent or an aprotic polar solvent may be used. Specifically, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 1,4-dioxane, monoglyme, diglyme, triglyme, tetraglyme, acetonitrile, benzonitrile, sulfolane, dimethylacetamide or dimethylsulfoxide may, for example, be used.
The formed fluorine-containing alkoxide is moved to an autoclave together with the reaction solvent without isolation, tetrafluoroethylene is introduced thereto at a temperature of from xe2x88x9210 to +50xc2x0 C., preferably from 0 to +30xc2x0 C., until the pressure becomes from 0.5 to 3.5 MPa, preferably from 1 to 2 MPa, and the reaction temperature is raised to a temperature of from 30 to 100xc2x0 C., preferably from 50 to 60xc2x0 C., so that the fluorine-containing alkoxide and tetrafluoroethylene are reacted to form the compound (f). The reaction time is from 30 minutes to 120 hours, preferably from about 10 hours to about 30 hours.
Then, the compound (f) is chlorinated so as to replace the two hydrogen atoms in the methylene group by chlorine atoms and to add chlorine atoms to the unsaturated group. As this chlorination, thermal chlorination or photo-chlorination is suitable, and particularly as the replacement by chlorine, photo-chlorination is preferred. Both replacement by chlorination and chlorine-addition reaction may be carried out by photo-chlorination. For example, it is carried out by passing chlorine gas through the solution of the compound (f) under irradiation with ultraviolet light. At the beginning of the reaction, chlorine addition to the unsaturated bond takes place, and as this reaction involves heat generation, it is preferred to carry out the reaction while cooling the system. The reaction temperature is suitably from 0 to 100xc2x0 C., and it is preferred to conduct the reaction by adjusting the temperature to be from 20 to 40xc2x0 C. The addition reaction is followed by a replacement of the methylene group by chlorine. This replacement reaction is usually carried out under irradiation with ultraviolet light at a reaction temperature higher than the above temperature, and the reaction temperature is suitably from 40 to 200xc2x0 C., preferably from 60 to 120xc2x0 C. By carrying out such a chlorination reaction, the compound (g) can be obtained. By adjusting the reaction conditions of the latter photo-chlorination reaction, partial chlorination of the methylene group can be achieved.
By partial fluorination of the dichloromethylene group adjacent to the ethereal oxygen atom in the compound (g) to replace only one chlorine atom by a fluorine atom (Macromolcules, 26, 5829 (1993) or U.S. Pat. No. 4,594,399), the compound (h) can be obtained. This partial fluorination can be carried out by treating the compound (g) with a mixture of antimony trifluoride and antimony pentachloride. This reaction can be carried out without a solvent, or can be carried out in an inert solvent such as a perfluorohydrocarbone solvent. The reaction temperature is suitably from 50 to 200xc2x0 C., preferably from 80 to 120xc2x0 C. One of the two chlorine atoms in the dichloromethylene group is easily replaced by a fluorine atom as compared with a chlorine atom in a chlorofluoromethylene group. The chlorofluoromethylene group after the replacement by a fluorine atom is less likely to further be fluorinated by the above fluorination method, similar to other chlorofluoromethylene groups.
By dehalogenation of the fluorine-containing compound (2), the fluorine-containing diene represented by the formula 1 can be obtained. In this case, even when X or Y in the fluorine-containing compound (2) is a halogen atom, no dehalogenation takes place under usual dehalogenation reaction conditions. This is attributable to the fact that the carbon atom adjacent thereto have no halogen atom of the same type. As a result, Z1 and Z2, and Z3 and Z4, undergo dehalogenation to produce two double bonds. This dehalogenation is carried out preferably in a polar solvent by using a dehalogenating agent.
The dehalogenating agent is a reaction agent acting on a halogen atom in a substrate and taking the halogen atom off. As the dehalogenating agent, preferred is zinc, sodium, magnetism, tin, copper, iron or another metal. As the dehalogenating agent, preferred is zinc from the viewpoint of reaction conditions such that a relatively low reaction temperature can be employed. As the polar solvent, an organic polar solvent such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1,4-dioxane, diglyme or methanol, or water, may, for example, be used preferably. Further, the molar ratio of the dehalogenating agent relative to the fluorine-containing compound (2) is suitably from 2 to 10 times, preferably from 5 to 8 times. The reaction temperature is suitably from 40 to 100xc2x0 C., preferably from 50 to 60xc2x0 C. The reaction is carried out usually by dropwise adding the fluorine-containing compound (2) in the presence of the dehalogenating agent and the solvent, and isolation of the reaction product is carried out by taking the reaction product off from the reaction system immediately after the reaction by distillation.
The fluorine-containing diene represented by the formula 1 of the present invention is polymerizable and is useful as a monomer for producing a fluorine-containing polymer. This fluorine-containing diene undergoes cyclic polymerization by the effect of a radical polymerization initiator to form a polymer having monomer units having a fluorine-containing alicyclic structure. Further, it can be copolymerized with another monomer. The another monomer copolymerizable with the fluorine-containing diene is not particularly limited so long as it is a radical-polymerizable monomer, and examples of which include a fluorine-containing monomer, a hydrocarbon type monomer and other monomers. Particularly preferred is an olefin such as ethylene or a fluoroolefin such as tetrafluoroethylene, chlorotrifluoroethylene or vinylidene fluoride. Further, the fluorine-containing diene may be copolymerized with a fluorine-containing vinyl ether type monomer such as perfluoro(alkyl vinyl ether), a fluorine-containing diene which may undergo cyclic polymerization (other than the compound represented by the formula 1) such as perfluoro(butenyl vinyl ether) or perfluoro(allyl vinyl ether), or a monomer having a fluorine-containing alicyclic structure such as perfluoro(2,2-dimethyl-1,3-dioxole) or perfluoro(2-methylene-4-methyl-1,3-dioxolane). These monomers may be used alone or in combination of at least two for copolymerization with the fluorine-containing diene.
The present invention further provides a homopolymer of the above fluorine-containing diene of the present invention, a copolymer of at least two types thereof, and a copolymer of the above fluorine-containing diene of the present invention with another monomer copolymerizable therewith. The proportion of the monomer units formed by polymerization of the fluorine-containing diene of the present invention in the polymer is preferably from 30 to 100 mol %, particularly preferably from 50 to 100 mol %, based on the total monomer units. Further, the molecular weight is preferably from 500 to 100,000, particularly preferably from 500 to 10,000.
As the radical polymerization initiator, a polymerization initiator which is used for an usual radical polymerization, such as an azo compound, an organic peroxide or an inorganic peroxide, may be used. Specific examples of the radical polymerization initiator include azo compounds such as diisopropyl peroxydicarbonate, 2,2xe2x80x2-azobis(2-amidinopropane)dihydrochloride, 4,4xe2x80x2-azobis(4-cyanopentanoic acid), 2,2xe2x80x2-azobis(4-methoxy-2,4-dimethylvaleronitrile) and 1,1xe2x80x2-azobis(1-cyclohexanecarbonitrile), organic peroxides such as benzoyl peroxide, perfluorobenzoyl peroxide, perfluorononanoyl peroxide, methyl ethyl ketone peroxide and diisopropyl peroxydicarbonate, and inorganic peroxides such as K2S2O8 and (NH4)2S2O8.
The polymerization method is not particularly limited also, and a so-called bulk polymerization of directly supplying the fluorine-containing diene to polymerization, a solution polymerization employing an organic solvent dissolving the fluorine-containing diene, such as a fluorinated hydrocarbon, a chlorinated hydrocarbon, a chlorinated fluorinated hydrocarbon, an alcohol or a hydrocarbon, a suspension polymerization carried out in an aqueous medium in the presence or absence of a proper organic solvent, or an emulsion polymerization carried out in an aqueous medium in the presence of an emulsifying agent, may, for example, be mentioned. The temperature and the pressure for the polymerization are not particularly limited, but preferably they are optionally set taking various factors such as boiling point of the fluorine-containing diene, the heat source required and removal of polymerization heat into consideration. For example, the polymerization temperature can suitably be set within a range of from 0 to 200xc2x0 C., and the polymerization is carried out particularly preferably at a temperature of from 30 to 100xc2x0 C. Further, the polymerization may be carried out under reduced pressure or under elevated pressure, and the polymerization can suitably be carried out under a level of from normal pressure to 10 MPa practically, preferably at a level of from normal pressure to 5 MPa.
The polymer of the present invention is characterized by that it is extremely excellent in transparency, it has a high elastic modulus, yield elongation in tension and breaking extension, it is less likely to break and is excellent in impact resistance, it has a high glass transition temperature and has a high heat resistance. Accordingly, the polymer of the present invention can be used as an optical resin material for optical components or optical devices such as optical fibers, optical waveguides and lenses, excellent in heat resistance by themselves. Further, the polymer of the present invention is characterized also by that it is optically transparent and has a refractive index higher than that of a conventional transparent fluororesin. Accordingly, by combining with e.g. a conventional transparent fluororesin having a low refractive index, high performance optical devices excellent in optical transparency, such as optical fibers or optical waveguides, can be obtained. For example, with respect to the optical fiber as disclosed in JP-A-8-5484, the polymer of the present invention can be used as an amorphous fluorine-containing polymer or as a low-molecular weight polymer (oligomer) to be used together with an amorphous fluorine-containing polymer.
Now, the present invention will be explained in further detail with reference to Examples and Comparative Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples.